1. Technical Field
The present invention relates to a liquid ejecting head, a liquid ejecting apparatus, and an actuator device.
2. Related Art
A part of a pressure generation chamber of an ink-jet recording head is made of a vibrating diaphragm. The pressure generation chamber is in communication with a nozzle orifice through which ink is ejected. A piezoelectric element deforms the vibrating diaphragm to pressurize ink that is retained in the pressure generation chamber. The ink-jet recording head ejects the pressurized ink from the nozzle orifices. Some ink-jet recording heads use a deformation-vibration-mode actuator device as such a piezoelectric element.
For example, a deformation-vibration-mode actuator device has piezoelectric elements manufactured as follows. A uniform piezoelectric material layer is formed over the entire surface of a vibrating diaphragm by means of a film deposition method. Then, by means of a lithography method, the piezoelectric material layer is separated into a plurality of area portions each of which has a shape corresponding to that of a pressure generation chamber. As a result, an individual piezoelectric element is formed for each of the plurality of pressure generation chambers. Such a piezoelectric element is susceptible to adverse effects from external environment such as, for example, moisture or the like, which causes damage to the piezoelectric element.
To protect a piezoelectric element against damage without obstructing the deformation operation of the piezoelectric element, the following head structure has been proposed in the art as disclosed in, for example, Japanese Patent No. 3552013 (refer to Page 4 and FIG. 4). In the disclosed head structure, a thin insulating film covers a partial region from the peripheral part of a surface of a second electrode inclusive to the side surfaces of a piezoelectric substance layer inclusive. The second electrode and the piezoelectric substance layer are components of the piezoelectric element. The insulating film is made of silicon oxide, silicon nitride, an organic material, or preferably, photosensitive polyimide.
However, the head structure disclosed in the above patent document has a disadvantage in that stress concentrates near an end of an exposed area when a piezoelectric element deforms. For this reason, there is a risk that the piezoelectric element is damaged due to stress concentration, which is a problem that remains to be solved.
The problem explained above is not unique to an ink-jet recording head that ejects ink. That is, the same problem could occur in various kinds of other liquid ejecting heads that eject liquid other than ink.